This invention relates to newly identified polynucleotides, polypeptides encoded by such polynucleotides, the use of such polynucleotides and polypeptides, as well as the production of such polynucleotides and polypeptides. The polypeptides of the present invention are human 7-transmembrane G-protein coupled receptors. More particularly, the polypeptides of the present invention are neuropeptide receptor polypeptides, sometimes hereinafter referred to as neuropeptide receptor polypeptides. The invention also relates to inhibiting the action of such polypeptides.
Obesity is the commonest nutritional disorder in Western societies. More than three in ten adult Americans weigh at least 20% in excess of their ideal body weight (Burroa, M., The New York Times, Jul. 17, 1994). Increased body weight is an important public health problem because it is associated with Type II diabetes, hypertension, hyperlipidemia and certain cancers (Grundy, S. M., and Barnett, J. P., Disease-a-Month, 36:645-696 (1990)).
Five single-gene mutations in the mouse obesity gene (ob) which result in an obese phenotype have been described (Friedman, J. M. and Leibel, R. L., Cell, 66:217-220 (1990)). The cloning and sequencing of the mouse ob gene and its human homologue have been reported (Zhang, Y., et al., Nature, 372:425-431 (1994)). The ob gene encodes a 4.5-kb adipose tissue mRNA with a highly conserved 167-amino-acid open reading frame. The predicted amino-acid sequence is 84% identical between human and mouse and has features of a secreted protein. The ob gene product may function as part of a signalling pathway from adipose tissue that acts to regulate the size of the body fat depot (id. 425).
Of the brain regions implicated in the regulation of feeding behavior, the ventromedial nucleus of the hypothalamus (VMH) is considered to be the most important satiety center in the central nervous system (CNS). The energy balance in mammals is therefore postulated to be controlled by a feedback loop in which the amount of stored energy is sensed by the hypothalamus, which adjusts food intake and energy expenditure to maintain a constant body weight (Ombeck, J. R., Yale J. Biol. Med., 20:545-552 (1948) and Kennedy, G. C., Proc. R. Soc. 148:578-592 (1953)). In the lipostasis theory, the size of the body fat depot is regulated by the CNS, with a product of body fat metabolism affecting energy balance by interacting with the hypothalamus (Kennedy, G. C., Proc. R. Soc. 148:578-592 (1953)).
The inability to identify the putative signal from fat has hindered the validation of the lipostasis theory. The possibility that at least one component of the signalling system circulates in the bloodstream was first suggested by Hervey (Dietrich, W., et al., Genetics, 131:423-447 (1992)), who showed that the transfer of blood from an animal with a VMH lesion across a vascular graft to an untreated animal (a parabiosis experiment) resulted in a reduction of food intake in the intact animal. It is now significant that there is evidence that the ob gene product is secreted, suggesting that ob may encode this circulating factor.
The ob signal may act directly or indirectly on the CNS to inhibit food intake and/or regulate energy expenditure as part of a homeostatic mechanism to maintain constancy of the adipose mass (Zhang, Y., et al., Nature, 372:425-431, 431 (1994)). The ob gene apparently encodes a protein secreted by fat, and mutations apparently prevent translation or expression of the gene (Rink, T., Nature, 372:406-407 (1994)).
Parabiosis experiments suggest that the ob receptor is encoded by the mouse db (diabetes) gene (Coleman, D. L., Diabetologia, 14:141-148 (1978)). Mice having a mutation in the db gene are also obese, with the defect possibly being a receptor defect. (Id. at 406).
Neuropeptide Y is similar to the ob gene product in that it mediates the feeding response. Neuropeptide Y acts on at least four types of neuropeptide Y receptors called Y1, Y2, Y3 and an atypical Y1 receptor, which mediates the feeding response stimulated by neuropeptide Y.
Neuropeptide Y has a wide range of biological functions. Neuropeptide Y is found to be widely distributed in the central nervous system (CNS) and the peripheral nervous system (PNS). In the PNS, neuropeptide Y is found in the noradrenergic sympathetic innervation of blood vessels and other smooth muscle tissues and in neurons within the enteric nervous system. Neuropeptide Y immunoreactive fibers also occur in the non-vascular smooth muscle, surrounding exocrine glands and surface epithelia. Neuropeptide Y also occurs in subpopulations of neurons and is generally co-localized with other neurotransmitters, particular noradrenaline.
In the CNS, neuropeptide Y is contained in GABAergic interneurons in higher centers and in predominantly catecholaminergic cells that project further caudally. For example, neuropeptide Y is contained in interneurons in the cortex, hippocampus, amygdala, basal forebrain and striatum, whereas in the brain stem, neuropeptide Y is contained in noradrenergic neurons of the A1 and A2 groups in the medulla, and the locus coeruleus (LC). In the hypothalamus, neuropeptide Y is found predominantly in the arcuate nucleus and lateral hypothalamus.
Within the peripheral nervous system, neuropeptide Y is present in postganglionic sympathetic nerves, and is co-localized as stated above with other neurotransmitters, including catecholamines. When used pharmacologically, neuropeptide Y has been shown to have a potent vasoconstrictor activity as well as dramatically potentiating the vasoconstriction caused by many other pressor agents. Particularly high concentrations of neuropeptide Y are found in the sympathetic nerves supplying the coronary, cerebral and renal vasculature and when infused into these vascular beds, neuropeptide Y causes prolonged vasoconstriction that is not reversed by adrenergic blocking agents. These observations have lead to the proposal that neuropeptide Y is the candidate transmitter for pathological vasospasm, a major cause of morbidity and mortality when involving the coronary and cerebral vessels.
Neuropeptide Y also appears to be involved in interaction with the renin angiotensin system. Neuropeptide Y containing sympathetic nerve terminals are found on the juxta-glomerular apparatus of the renal cortex and neuropeptide Y influences renin release. These data, together with the demonstration of all durations in neuropeptide Y concentrations in hypertensive animal models and the pressor response to infusion of the peptide, have resulted in implications of this peptide in hypertension.
Within the central nervous system neuropeptide Y is located predominantly within interneurons where it appears to have a regulatory role. It therefore has widespread and diverse effects including effects on memory and a possible role in Alzheimer""s disease. Neuropeptide Y is the most potent known substance to cause an increase in feeding and may play a role in the genetic basis of Type II Diabetes Mellitus. Neuropeptide Y may also play a role as a regulatory agent and pituitary function as well as potential neuromodulatory function in stress responses and in reproductive function.
In accordance with one aspect of the present invention, there are provided novel mature receptor polypeptides as well as biologically active and diagnostically or therapeutically useful fragments, analogs and derivatives thereof. The receptor polypeptides of the present invention are of human origin.
In accordance with another aspect of the present invention, there are provided isolated nucleic acid molecules encoding the receptor polypeptides of the present invention, including mRNAs, DNAs, cDNAs, genomic DNA as well as antisense analogs thereof and biologically active and diagnostically or therapeutically useful fragments thereof.
In accordance with a further aspect of the present invention, there are provided processes for producing such receptor polypeptides by recombinant techniques comprising culturing recombinant prokaryotic and/or eukaryotic host cells, containing nucleic acid sequences encoding the receptor polypeptides of the present invention, under conditions promoting expression of said polypeptides and subsequent recovery of said polypeptides.
In accordance with yet a further aspect of the present invention, there are provided antibodies against such receptor polypeptides.
In accordance with another aspect of the present invention there are provided methods of screening for compounds which bind to and activate or inhibit activation of the receptor polypeptides of the present invention.
In accordance with still another embodiment of the present invention there are provided processes of administering compounds to a host which bind to and activate the receptor polypeptide of the present invention which are useful in the prevention and/or treatment of obesity, hyperlipidemia, certain cancers, to stimulate neuronal growth, to regulate neurotransmission, to enhance activity levels and utilization of ingested foods.
In accordance with another aspect of the present invention there is provided a method of administering the receptor polypeptides of the present invention via gene therapy to treat conditions related to underexpression of the polypeptides or underexpression of a ligand to the receptor polypeptide.
In accordance with still another embodiment of the present invention there are provided processes of administering compounds to a host which bind to and inhibit activation of the receptor polypeptides of the present invention which are useful in the prevention and/or treatment of Alzheimer""s disease, Type II Diabetes Mellitus, epilepsy, stress, anxiety, hypertension, cardiovascular disease, psychotic conditions and obesity caused by neuropeptide Y.
In accordance with yet another aspect of the present invention, there are provided nucleic acid probes comprising nucleic acid molecules of sufficient length to specifically hybridize to the polynucleotide sequences of the present invention.
In accordance with still another aspect of the present invention, there are provided diagnostic assays for detecting diseases related to mutations in the nucleic acid sequences encoding such polypeptides and for detecting an altered level of the soluble form of the receptor polypeptides.
In accordance with yet a further aspect of the present invention, there are provided processes for utilizing such receptor polypeptides, or polynucleotides encoding such polypeptides, for in vitro purposes related to scientific research, synthesis of DNA and manufacture of DNA vectors.
These and other aspects of the present invention should be apparent to those skilled in the art from the teachings herein.